Prince William has spoken of his fear that elephants, rhinos and tigers could be extinct by the time his children are in their 20s.

In an passionate speech at a conference in London, the Duke of Cambridge said more must be done to stamp out the illegal wildlife trade - and warned it funds criminal networks and threatens the livelihoods of impoverished communities.

Describing a recent trip to Africa, where he witnessed conservation efforts first hand, he said: "Some of the rhinos I saw are under such threat that they have more bodyguards than I do."

Although Prince William praised the progress made in recent years, he warned against complacency and detailed the human cost of protecting wildlife.

"Over 1,000 rangers have been killed in the line of duty in the past decade. Poaching levels may well be decreasing in some areas but overall they remain too high," he said.

Image:Prince William said it is 'heartbreaking' to think elephants may be extinct by the time his children are in their 20s

The Duke of Cambridge was speaking at the Illegal Wildlife Conference - the largest of its kind to ever be held.

He said most of the world's major banks have now committed to improve how they identify, track and report suspicious financial activity related to the illegal wildlife trade - and urged these institutions to treat it as a "serious financial crime".

Prince William added: "As the ivory market is closing down in some countries it is being displaced elsewhere. Pangolin scales, rhino horns and body parts of big cats are still easy to find in street stalls all around the world.

"We are not yet seeing enough criminal convictions for wildlife offences, and all too often punishments are too lenient. And all this means that thousands of local communities are deprived of their most valuable natural resources and a route of poverty."

Reminding the audience of the real threat of extinction that elephants, rhino and tigers in the wild face, he said: "I for one am not willing to look my children in the eye and say that we were the generation that let this happen on our watch."

Image:The Duke of Cambridge warned against complacency during his impassioned speech

The Duke of Cambridge was joined at the conference by Foreign Secretary Jeremy Hunt, who said: "The criminal gangs who smuggle horns and tusks pose one of the greatest threats to the survival of wildlife."

"They target some of the poorest countries in the world spreading corruption and depriving governments of desperately needed revenues that could be used for schools and hospitals."

Mr Hunt said the UK has launched an initiative to help countries in Africa and Asia launch investigations into illegal activity and seize assets - with ivory sales now banned in the UK.